It may be desirable to control the in-rush current to a starter motor for an engine of a motor vehicle by providing a resistance arranged in series with the starter motor. For a conventional or ‘static’ stop-start system, the vehicle is stationary when the engine is stopped and started and so a significant voltage drop due to a relatively high in-rush current is permissible since a relatively high amount of torque may be used to start the vehicle. It is desirable to permit a relatively high in-rush current to occur as this will result in rapid starting of the engine which is required for a normal ‘static’ automatic start operation of the motor vehicle.
However, if the motor vehicle is operated in an automatic stop-start mode when the vehicle is moving in a so called ‘dynamic’ stop-start mode then the relatively high in-rush current normally used for a ‘static’ start may result in an undesirable voltage drop. This is because some vehicle systems such as anti-lock braking systems and electronically controlled steering can be degraded when the system voltage drops below a predetermined level.
It may therefore be desirable to use a high level of in-rush current resistance when conducting a ‘dynamic’ automatic restart as the time taken to restart the engine is less critical and the need to prevent undesirable system voltage drop is paramount in order to maintain operation of other vehicle systems. However, if a lower level of in-rush current is continuously set so as to prevent an undesirable voltage drop for ‘dynamic’ automatic restarts, then the start-up performance of the motor vehicle may be slower than is desired for ‘static’ automatic restarts.
It is an object of the description to provide a method and apparatus for providing acceptable restart performance while maintaining operation of other vehicle systems.
The inventors herein have recognized the above-mentioned disadvantages and have developed an a method of limiting the in-rush current to a starter motor of an engine of a vehicle comprising: providing at least two levels of in-rush current restriction and applying one of the at least two levels of in-rush current restriction to the starter motor in response to the present operating speed of the vehicle.
By applying different levels of in-rush current to a starter motor that engages an engine during engine starting, it may be possible to provide a vehicle system voltage that allows for continued operation of other vehicle electrical power consumers during engine cranking. For example, in-rush current supplied to a starter motor during engine cranking can be reduced when a vehicle speed is above a threshold level to allow electrically assisted brakes to operate. In this way, operation of vehicle electrical power consumers can continue even during engine cranking.
The present description may provide several advantages. Specifically, the approach may allow additional vehicle electrical consumers to operate during engine cranking. Further, the approach can provide different levels of in-rush current for different vehicle speeds so that when the engine is started via a starter and vehicle kinetic energy (e.g., rotating the engine via vehicle wheel torque) a desirable level of starter current is provided. Further still, the approach provides for a higher level of starter current during cold engine starting.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The drawings included herein serve merely for the explanation of the description, and do not restrict the description.